Bacteriological titration tray

ABSTRACT

A MOLDED PLASTIC TITRATION TRAY CONTAINING A LARGE NUMBER OF SMALL OPEN TEST CUPS SERVING AS INDIVIDULA TEST TUBES AND WHICH ARE INTEGRAL WITH THE TRAY AND PROJECT DOWNWARDLY FROM THE TRAY EXCEPT FOR A LIP AT THE TOP OF EACH CUP WHICH PROJECTS ABOVE THE SURFACE OF THE TRAY TO PREVENT SERUM OR SOLUTION SPILLED ON THE TRAY SURFACE FROM CONTAMINATING THE TRAY CONTENTS OF THE CUP. IN ONE MODIFICATION THRER IS A SMALL HOLE IN THE BOTTOM OF EACH CUP, SMALL ENOUGH SO THAT SURFACE TENSION PREVENTS THE FLUID CONTENTS OF THE CUP FROM FLOWING THROUGH THE HOLE, BUT THE CONENTS CAN BE DISCHARGED AT WILL BY APPLYING A SONIC PROBE OR AIR PRESSURE TO THE CUP.

Y A R T N O I m R Ln 5T s L m m AU L 0 I R E T C A B Filed Jan.

INVENTOR Milton Kass/er ATTORNEY United States Patent 3,785,928BACTERIOLOGICAL TITRATION TRAY Milton Kessler, 6690 Harrington Ave.,Youngstown, Ohio 44512 Filed Jan. 27, 1971, Ser. No. 110,108 Int. Cl.C12k N US. Cl. 195-140 2 Claims ABSTRACT OF THE DISCLOSURE A moldedplastic titration tray containing a large number of small open test cupsserving as individual test tubes and which are integral with the trayand project downwardly from the tray except for a lip at the top of eachcup which projects above the surface of the tray to prevent serum orsolution spilled on the tray surface from contaminating the traycontents of the cup. In one modification there is a small hole in thebottom of each cup, small enough so that surface tension prevents thefluid contents of the cup from flowing through the hole, but thecontents can be discharged at will by applying a sonic probe or airpressure to the cup.

Many standard laboratory procedures in both biological research andmedical laboratories require the use of large numbers of test tubes ineach of which a small sample of fluid material is placed for testpurposes. A common device for such use is a titration tray, which istypically a small plastic tray measuring approximately four by sixinches, and containing a number of rows of small cups projectingdownwardly from the tray surface, typically eight rows of twelve cupseach. These are used in place of test tubes for assaying virus,measuring antibodies and tissue culture, serum dilutions, and many typesof spot tests. In use, a small amount of each solution being tested isdropped into each cup by means of a pipette or medical dropper orsimilar device, and it is, of course, important that these solutions bekept entirely independent of each other, as even a trace ofcontamination from one solution to another will invalidate the testresults. With the present type of tray, if there is any carelessness infilling the cups, so that one overflows, this overflow will spread onthe surface of the tray to adjacent cups, thereby contaminating them.This problem is solved, according to the present invention, by providinga raised lip around each cup, so that material spilled on the surface ofthe tray cannot readily enter adjacent cups. It is also desirable forsome testing purposes to transfer the contents of individual cups toother cups in a different tray, and the present invention provides anovel method for expeditiously doing this by means of a small hole inthe bottom of each cup, too small to normally permit the contents toflow through the hole because of the surface tension of the liquid; byapplying a sonic or ultra-sonic prove to the individual cups, or byapplying air pressure to the individual cups, the surface tension can bebroken and the contents made to flow readily through the small apertureinto another cup placed below the first cup. This can be done either tothe entire contents of a tray, each cup pouring its contents intoanother cup in a similar tray placed below the first, or else can bedone to individual cups selectively.

The specific nature of the invention, as well as other objects andadvantages thereof, will clearly appear from a description of apreferred embodiment as shown in the accompanying drawing, in which:

FIG. 1 is a plan view of a titration tray showing a typical arrangementof the cups; and

FIG. 2 is a sectional view taken along line 2-2 of FIG. 1, showing bothtypes of cups and also a typical stacking arrangement for the trays.

Referring to the drawings, a standard form of titra- 3,785,928 PatentedJan. 15, 1974 tion tray 2 is made of clear plastic having 96 cups 3arranged in eight rows of twelve cups each, and typically provided withnumbers 1 12 to designate the vertical rows and letters A, B H toindicate the horizontal rows, whereby the location of any individual cupcan be designated by the combination of a number and a letter. Theentire tray is preferably formed by an injection molding operation, thetechnique of which is well known. The entire tray is usually only aboutfour by six inches in size, and the individual cups are in the order of0.25 inch diameter by approximately A inch deep. One novel feature ofthe present tray is that each individual cup 3 is provided with a raisedrim 4 which extends above the surface 2 of the tray. While :a carefuloperator can usually fill each cup individually without spillage,sometimes there is a slight overfilling, and a small amount of thematerial then spills out onto the surface 2 of the tray. In the knowntypes of tray, where the cup is flush with the surface of the tray,there is nothing to prevent this material as it spreads from spillingover into an adjacent cup, with resultant contamination which may spoilthe test being made. The raised lip 4 of the present cups minimizes thispossibility, as a small amount of spillage may spread somewhat on thesurface of the tray, but will not enter into the adjacent cups becauseof the raised lips. For standard usage, the upper and lower trays shownin FIG. 2 are identical, except that the upper set is provided with aperforation of approximately pinhole size in the bottom, while the lowerset is unperforated. The pinholes are sufliciently small so that thefluid 7 disposed in the cup 3 will not flow through the pinholenormally, because of the surface tension of the fluid. However, if ahigh frequency vibrating device such as an ultra-sonic probe 8, which isa known device used in spot welding of plastic materials, is applied tothe rim 4 of the cup 3, the resultant vibrations will cause the contentsof the cup to be discharged into any suitable container, which willusually be a similar tray placed beneath the tray having the perforatedcups. The trays are provided with side walls 9 having lips 11 so thatthey can be stacked one above the other, whereby the contents of eachcup will be dis charged into the correspondingly numbered cup of thelower tray. The lower tray may have imperforated cups, or if desired,may also contain perforate cups for subsequent discharge of the contentsinto still another container.

For use with the ultra-sonic probe, the perforate-cup trays shouldpreferably be made of a fairly hard plastic material so that the sonicvibrations will be transmitted through the material. If the entire trayis made of such material, all of the contents of the cups can besimultaneously emptied into a lower tray or any other desired container;however, for many test purposes, it may be desirable to empty thecontents of the cups individually, and for this purpose, the individualcups 3 are preferably made of a relatively rigid plastic material, asindicated by the section lines in FIG. 2, while the rest of the tray ismade of a softer and deaded plastic material so that it will nottransmit vibrations, whereby when the probe is touched to eachindividual cup it can be emptied without affecting the adjacent cups dueto the vibration insulating qualities of the softer plastic material.This can be readily accomplished by dual-injection techniques which areknown in the art whereby different materials may be simultaneouslymolded to produce a unitary object having both soft and hard portions.

Another way of emptying individual cups is to use a pressure bulb 12having a soft rubber or rubber-like tube of the proper diameter toencompass individual cups, whereby a slight finger pressure on the bulb12 will produce a suflicient increase in air pressure on the top of thefluid contained in the cup so that it is immediately emptied through theaperture 6 into the lower cup or container.

Particularly in the case where the trays are made of a single material,this may be a very thin plastic sheet material, which enables the entiretray to be made so inexpensively that it can be thrown away after eachuse, thus disposing of any need for sterilizing between uses. If thetrays are to be re-usable, then they will be made of heavierconstruction and a more rigid material which can stand the sterilizingtemperatures which may be necessary. It is apparent that the pinhole inthe cup has utility apart from the lip.

I claim:

1. A bateriological titration tray formed of a single sheet of plasticmaterial having (a) a flat horizontal tray-surface having a number ofsmall test cups which are integral with the tray surface and whichproject generally downwardly from the tray surface,

(b) said sheet around the mouth of each said cup having a raised lip atthe top of each cup, which lip projects above the surface of the tray toprevent liquid spilled on the tray surface from readily spreading oversaid surface into said cups,

(c) wherein at least some of said cups have a small pinhole perforationat the bottom,

(d) said pinhole perforation being sufliciently small so that surfacetension will normally prevent fluid in said perforated cups from flowingout through the perforation, but large enough so that when the surfacetension is broken, the fluid will flow through the pinhole.

2. A bacteriological titration tray having (a) a flat tray surface ofsheet material having a number of small open test cups which areintegral with the tray surface and project generally downwardly from thetray surface,

(b) wherein at least some of said cups have a small pinhole perforationat the bottom,

(0) said pinhole perforation being sufficiently small so that thesurface tension will normally prevent fluid in said perforated cups fromflowing out through the perforations, but large enough so that when thesurface tension is broken, the fluid will flow through the pinhole.

References Cited UNITED STATES PATENTS 3,356,462 12/1967 Cooke et al195139 LE 3,649,464 3/1972 Freeman 195-140 A. LOUIS MONACELL, PrimaryExaminer R. J. WARDEN, Assistant Examiner US. Cl. X.R. 23-292; -139

